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Office of Audit Operations & Special Reviews

Assistant Inspector General for Audit Operations & Special Reviews

Tiffany Mostert

Tiffany Mostert

As Assistant Inspector General for Audit Operations and Special Reviews, Tiffany Mostert is responsible for overseeing DOT OIG’s audit support functions, including planning, policies, and procedures; support and audit work conducted by DOT OIG experts in economics, statistics, and engineering; and special reviews. She also fosters cooperative relationships both within DOT OIG and Department-wide.

Ms. Mostert joined DOT OIG in 2011 as an analyst in New York, where she conducted program audits of the Federal Transit Administration. In 2014, she was promoted to Project Manager in the Office of Surface Transportation Audits. When she became a Program Director in 2017, she relocated to Washington, DC, where she led project managers and audit teams conducting a wide variety of surface transportation program audits. As Program Director, she managed a broad portfolio of complex audit work, including reviews of the Department’s oversight of billions of dollars in funding provided for Hurricane Sandy and COVID-19 emergency relief, as well as hundreds of billions of dollars provided to DOT by the Infrastructure Investment and Jobs Acts. Over the course of her career, Ms. Mostert’s work has resulted in numerous audit reports, recommendations for program improvement, contributions to congressional briefings and testimonies, and more than a billion dollars in monetary findings. She also made significant contributions to improving internal DOT OIG initiatives related to hiring, staffing, training, policies, and processes.

Ms. Mostert began her career at the U.S. Government Accountability Office in Washington, DC. In her over 20 years of Federal service, she has received multiple team and individual awards, including the prestigious Secretary of Transportation’s Meritorious Service Award in 2022. Ms. Mostert received her master’s in public administration from the Maxwell School of Citizenship and Public Affairs at Syracuse University and a bachelor of arts in communication studies from The College of New Jersey. 


Chief Economist

Betty Krier

Betty KrierAs Chief Economist, Betty Krier leads the DOT OIG economics group in conducting often complex analyses to assess the efficiency and effectiveness of departmental programs and regulatory actions, as well as to examine issues of potential departmental concern. Examples of economics group work include assessments of the relative efficiency of different FAA air traffic control towers, safety and income impacts of trucker wait times at shipping and receiving facilities, effects of the Tarmac Delay Rule on airline cancellations, and potential anticompetitive practices in bidding on highway procurements.

Ms. Krier joined DOT OIG as an economist in 2004 and was soon promoted to Senior Economist and then Supervisory Economist. In addition to planning and directing economics group work, Ms. Krier oversees the day-to-day work of the multiple audit projects handled by the group at any time, ensuring high standards of quality and productivity. She routinely meets with internal and external stakeholders, including DOT OIG officials and Congress, to report on economics group findings and recommendations. In addition, she has made presentations to representatives of European and other North American governments. Previously, Ms. Krier worked in consulting and for investment banks.

Ms. Krier has won numerous DOT OIG awards, a Council of the Inspectors General on Integrity and Efficiency award, and in 2017 received the Secretary’s Meritorious Achievement for developing innovative econometric methods in audit work in support of DOT OIG’s goals.

Ms. Krier earned her undergraduate degree from Harvard University and did her graduate work at the Massachusetts Institute of Technology.